Android example source code file (BoringLayout.java)

This example Android source code file (BoringLayout.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

alignment, android, boringlayout, dir_left_to_right, directions, drawing, first_right_to_left, graphics, metrics, object, override, paint, path, spanned, string, textpaint, ui, util

The BoringLayout.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.text;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.text.style.ParagraphStyle;
import android.util.FloatMath;

/**
 * A BoringLayout is a very simple Layout implementation for text that
 * fits on a single line and is all left-to-right characters.
 * You will probably never want to make one of these yourself;
 * if you do, be sure to call {@link #isBoring} first to make sure
 * the text meets the criteria.
 * <p>This class is used by widgets to control text layout. You should not need
 * to use this class directly unless you are implementing your own widget
 * or custom display object, in which case
 * you are encouraged to use a Layout instead of calling
 * {@link android.graphics.Canvas#drawText(java.lang.CharSequence, int, int, float, float, android.graphics.Paint)
 *  Canvas.drawText()} directly.</p>
 */
public class BoringLayout extends Layout implements TextUtils.EllipsizeCallback {
    public static BoringLayout make(CharSequence source,
                        TextPaint paint, int outerwidth,
                        Alignment align,
                        float spacingmult, float spacingadd,
                        BoringLayout.Metrics metrics, boolean includepad) {
        return new BoringLayout(source, paint, outerwidth, align,
                                spacingmult, spacingadd, metrics,
                                includepad);
    }

    public static BoringLayout make(CharSequence source,
                        TextPaint paint, int outerwidth,
                        Alignment align,
                        float spacingmult, float spacingadd,
                        BoringLayout.Metrics metrics, boolean includepad,
                        TextUtils.TruncateAt ellipsize, int ellipsizedWidth) {
        return new BoringLayout(source, paint, outerwidth, align,
                                spacingmult, spacingadd, metrics,
                                includepad, ellipsize, ellipsizedWidth);
    }

    /**
     * Returns a BoringLayout for the specified text, potentially reusing
     * this one if it is already suitable.  The caller must make sure that
     * no one is still using this Layout.
     */
    public BoringLayout replaceOrMake(CharSequence source, TextPaint paint,
                                      int outerwidth, Alignment align,
                                      float spacingmult, float spacingadd,
                                      BoringLayout.Metrics metrics,
                                      boolean includepad) {
        replaceWith(source, paint, outerwidth, align, spacingmult,
                    spacingadd);

        mEllipsizedWidth = outerwidth;
        mEllipsizedStart = 0;
        mEllipsizedCount = 0;

        init(source, paint, outerwidth, align, spacingmult, spacingadd,
             metrics, includepad, true);
        return this;
    }

    /**
     * Returns a BoringLayout for the specified text, potentially reusing
     * this one if it is already suitable.  The caller must make sure that
     * no one is still using this Layout.
     */
    public BoringLayout replaceOrMake(CharSequence source, TextPaint paint,
                                      int outerwidth, Alignment align,
                                      float spacingmult, float spacingadd,
                                      BoringLayout.Metrics metrics,
                                      boolean includepad,
                                      TextUtils.TruncateAt ellipsize,
                                      int ellipsizedWidth) {
        boolean trust;

        if (ellipsize == null || ellipsize == TextUtils.TruncateAt.MARQUEE) {
            replaceWith(source, paint, outerwidth, align, spacingmult,
                        spacingadd);

            mEllipsizedWidth = outerwidth;
            mEllipsizedStart = 0;
            mEllipsizedCount = 0;
            trust = true;
        } else {
            replaceWith(TextUtils.ellipsize(source, paint, ellipsizedWidth,
                                           ellipsize, true, this),
                        paint, outerwidth, align, spacingmult,
                        spacingadd);

            mEllipsizedWidth = ellipsizedWidth;
            trust = false;
        }

        init(getText(), paint, outerwidth, align, spacingmult, spacingadd,
             metrics, includepad, trust);
        return this;
    }

    public BoringLayout(CharSequence source,
                        TextPaint paint, int outerwidth,
                        Alignment align,
                        float spacingmult, float spacingadd,
                        BoringLayout.Metrics metrics, boolean includepad) {
        super(source, paint, outerwidth, align, spacingmult, spacingadd);

        mEllipsizedWidth = outerwidth;
        mEllipsizedStart = 0;
        mEllipsizedCount = 0;

        init(source, paint, outerwidth, align, spacingmult, spacingadd,
             metrics, includepad, true);
    }

    public BoringLayout(CharSequence source,
                        TextPaint paint, int outerwidth,
                        Alignment align,
                        float spacingmult, float spacingadd,
                        BoringLayout.Metrics metrics, boolean includepad,
                        TextUtils.TruncateAt ellipsize, int ellipsizedWidth) {
        /*
         * It is silly to have to call super() and then replaceWith(),
         * but we can't use "this" for the callback until the call to
         * super() finishes.
         */
        super(source, paint, outerwidth, align, spacingmult, spacingadd);

        boolean trust;

        if (ellipsize == null || ellipsize == TextUtils.TruncateAt.MARQUEE) {
            mEllipsizedWidth = outerwidth;
            mEllipsizedStart = 0;
            mEllipsizedCount = 0;
            trust = true;
        } else {
            replaceWith(TextUtils.ellipsize(source, paint, ellipsizedWidth,
                                           ellipsize, true, this),
                        paint, outerwidth, align, spacingmult,
                        spacingadd);


            mEllipsizedWidth = ellipsizedWidth;
            trust = false;
        }

        init(getText(), paint, outerwidth, align, spacingmult, spacingadd,
             metrics, includepad, trust);
    }

    /* package */ void init(CharSequence source,
                            TextPaint paint, int outerwidth,
                            Alignment align,
                            float spacingmult, float spacingadd,
                            BoringLayout.Metrics metrics, boolean includepad,
                            boolean trustWidth) {
        int spacing;

        if (source instanceof String && align == Layout.Alignment.ALIGN_NORMAL) {
            mDirect = source.toString();
        } else {
            mDirect = null;
        }

        mPaint = paint;

        if (includepad) {
            spacing = metrics.bottom - metrics.top;
        } else {
            spacing = metrics.descent - metrics.ascent;
        }

        if (spacingmult != 1 || spacingadd != 0) {
            spacing = (int)(spacing * spacingmult + spacingadd + 0.5f);
        }

        mBottom = spacing;

        if (includepad) {
            mDesc = spacing + metrics.top;
        } else {
            mDesc = spacing + metrics.ascent;
        }

        if (trustWidth) {
            mMax = metrics.width;
        } else {
            /*
             * If we have ellipsized, we have to actually calculate the
             * width because the width that was passed in was for the
             * full text, not the ellipsized form.
             */
            synchronized (sTemp) {
                mMax = (int) (FloatMath.ceil(Styled.measureText(paint, sTemp,
                                                source, 0, source.length(),
                                                null)));
            }
        }

        if (includepad) {
            mTopPadding = metrics.top - metrics.ascent;
            mBottomPadding = metrics.bottom - metrics.descent;
        }
    }

    /**
     * Returns null if not boring; the width, ascent, and descent if boring.
     */
    public static Metrics isBoring(CharSequence text,
                                   TextPaint paint) {
        return isBoring(text, paint, null);
    }

    /**
     * Returns null if not boring; the width, ascent, and descent in the
     * provided Metrics object (or a new one if the provided one was null)
     * if boring.
     */
    public static Metrics isBoring(CharSequence text, TextPaint paint,
                                   Metrics metrics) {
        char[] temp = TextUtils.obtain(500);
        int len = text.length();
        boolean boring = true;

        outer:
        for (int i = 0; i < len; i += 500) {
            int j = i + 500;

            if (j > len)
                j = len;

            TextUtils.getChars(text, i, j, temp, 0);

            int n = j - i;

            for (int a = 0; a < n; a++) {
                char c = temp[a];

                if (c == '\n' || c == '\t' || c >= FIRST_RIGHT_TO_LEFT) {
                    boring = false;
                    break outer;
                }
            }
        }

        TextUtils.recycle(temp);

        if (boring && text instanceof Spanned) {
            Spanned sp = (Spanned) text;
            Object[] styles = sp.getSpans(0, text.length(), ParagraphStyle.class);
            if (styles.length > 0) {
                boring = false;
            }
        }

        if (boring) {
            Metrics fm = metrics;
            if (fm == null) {
                fm = new Metrics();
            }
    
            int wid;

            synchronized (sTemp) {
                wid = (int) (FloatMath.ceil(Styled.measureText(paint, sTemp,
                                                text, 0, text.length(), fm)));
            }
            fm.width = wid;
            return fm;
        } else {
            return null;
        }
    }

    @Override public int getHeight() {
        return mBottom;
    }

    @Override public int getLineCount() {
        return 1;
    }

    @Override public int getLineTop(int line) {
        if (line == 0)
            return 0;
        else
            return mBottom;
    }

    @Override public int getLineDescent(int line) {
        return mDesc;
    }

    @Override public int getLineStart(int line) {
        if (line == 0)
            return 0;
        else
            return getText().length();
    }

    @Override public int getParagraphDirection(int line) {
        return DIR_LEFT_TO_RIGHT;
    }

    @Override public boolean getLineContainsTab(int line) {
        return false;
    }

    @Override public float getLineMax(int line) {
        return mMax;
    }

    @Override public final Directions getLineDirections(int line) {
        return Layout.DIRS_ALL_LEFT_TO_RIGHT;
    }

    public int getTopPadding() {
        return mTopPadding;
    }

    public int getBottomPadding() {
        return mBottomPadding;
    }

    @Override
    public int getEllipsisCount(int line) {
        return mEllipsizedCount;
    }

    @Override
    public int getEllipsisStart(int line) {
        return mEllipsizedStart;
    }

    @Override
    public int getEllipsizedWidth() {
        return mEllipsizedWidth;
    }

    // Override draw so it will be faster.
    @Override
    public void draw(Canvas c, Path highlight, Paint highlightpaint,
                     int cursorOffset) {
        if (mDirect != null && highlight == null) {
            c.drawText(mDirect, 0, mBottom - mDesc, mPaint);
        } else {
            super.draw(c, highlight, highlightpaint, cursorOffset);
        }
    }

    /**
     * Callback for the ellipsizer to report what region it ellipsized.
     */
    public void ellipsized(int start, int end) {
        mEllipsizedStart = start;
        mEllipsizedCount = end - start;
    }

    private static final char FIRST_RIGHT_TO_LEFT = '\u0590';

    private String mDirect;
    private Paint mPaint;

    /* package */ int mBottom, mDesc;   // for Direct
    private int mTopPadding, mBottomPadding;
    private float mMax;
    private int mEllipsizedWidth, mEllipsizedStart, mEllipsizedCount;

    private static final TextPaint sTemp =
                                new TextPaint();

    public static class Metrics extends Paint.FontMetricsInt {
        public int width;
        
        @Override public String toString() {
            return super.toString() + " width=" + width;
        }
    }
}